The present invention relates to optical spectroscopic detectors and especially to multichannel spectroscopic measurement units.
The optical energy detection at a particular optical wavelength is used for a number of different purposes. Often, detected light intensity at different wavelengths is used to produce a ratio that gives information about a process, such a paper making processes. Typically, one of the wavelengths is related to a process variation such as water level and another is a reference wavelength related to process conditions.
FIG. 1A shows a typical prior art system. In this system, light from optical path 102 is sent to an optical splitter 104, filter 106, focusing optics 108, to the optical energy detector 110. The optical energy detector 110 is adapted to detect light at the wavelength D1. Some of the light passes through the splitter 104; this light goes to the second splitter 112. Half of the light is sent to the optical energy detector 114. The other portion of the light is sent to the optical splitter 116. The optical splitter 116 sends half of the light to the optical energy detector 118 and half of the light to the optical mirror 120. The mirror 120 sends the light to the optical energy detector 122. In this example, more light is sent to the optical energy detector 110 than is sent to the other optical energy detectors 114, 118 and 122.
FIG. 1B illustrates a prior art system in which light from a fiber optic cable is split. In this example, the optical fiber 128 is split into three branches that equally distribute the light to the optical energy detectors 130, 132, 134 and 136 after passing through filters 138, 140, 142 and 143.